Optical interconnection devices can be used to optically connect a first optical waveguide to a second optical waveguide, or a first set of optical waveguides to a second set of optical waveguides. The optical waveguides can be optical fibers. Such optical interconnection devices are referred to in the art as fiber-to-fiber connectors.
Optical interconnection devices can also be used to optically connect one or more optical fibers to one or more optical waveguides of a planar light circuit (PLC) or an integrated photonic device such as a photonic integrated circuit (PIC). Such optical interconnection devices are referred to in the art as fiber-to-chip connectors. Because optical fibers have relatively small core diameters, e.g., on the order of 10 microns for single mode fibers, fiber-to-fiber connectors and fiber-to-chip connectors need to establish alignment with their counterpart connector or waveguide connector to submicron accuracy.
A conventional way of achieving such accuracy when optically connecting optical fiber arrays is to use multifiber push-on/pull-off (MPO) connectors that employ mechanical transfer (MT) ferrules as the main component. The MT ferrule is made of a polymer thermoplastic material such as polyphenylene sulfide (PPS) or thermoset materials. The component cost of MTP connectors is typically several dollars, which is relatively expensive. Furthermore, the coefficient of thermal expansion (CTE) of the MT ferrule differs substantially from silicon. This large difference in the CTE values of the two materials can create alignment issues (e.g., unacceptable lateral misalignment between cores) when connecting an MPO connector to a silicon-based PIC. For example, over a temperature range of 60° C., the CTE difference between the polymer thermoplastic of the MPO connectors and the silicon-based PIC can result in a maximum misalignment of 0.8 microns or greater over a linear array of 12 fibers spaced on 250 micrometer pitch, which when compounded with other sources of misalignment can lead to significantly higher insertion loss.
As greater and greater demands are placed on fiber-to-fiber and fiber-to-chip connectors with respect to size (form factor), alignment tolerances and insertion loss for both fiber-to-fiber and fiber-to-chip applications, it is becoming increasingly problematic to employ conventional optical fiber connectors.